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(Pb1−x−ySrxBay)(Zr0.976−zTizNb0.024)O3 solid solutions have been investigated to understand the relationship between structural changes caused by isovalent strontium and barium substitution on the A‐site and dielectric and piezoelectric properties. As strontium and barium were substituted for lead, the zirconium:titanium (Zr:Ti) ratio was modified so that all compositions had an optimized piezoelectric coefficient (d33). The value of d33 was at a maximum in the tetragonal phase near, but not at, the morphotropic‐phase boundary (MPB). The real MPB was taken as the Zr:Ti ratio at which X‐ray diffraction patterns appeared either pseudocubic or a mixture of rhombohedral and tetragonal. As strontium content increased, optimized d33 also increased from 410 pC/N (x= 0) to 640 pC/N (x= 0.12), commensurate with a decrease in the paraelectric‐to‐ferroelectric phase transition temperature (TC) from 350°C (x= 0) to 175°C (x= 0.12). However, for ceramics where x > 0.12, optimized d33 decreased even though the phase‐transition temperature was ∼150°C. Low strontium concentration ceramics (x= 0–0.08) contained 80 nm ferrroelectric domains typical of PZT, but high strontium concentration ceramics (x= 0.12–0.16) contained fine‐scale domains (20 nm) in some regions of the microstructure. In addition, [110] pseudocubic electron diffraction patterns revealed superlattice reflections at 1/2{hkl} positions associated with rotations of the octahedra in antiphase. Co‐doping ceramics with strontium (x= 0.06) and barium (y= 0.06) resulted in the disappearance of the 1/2{hkl} reflections. Optimized d33 (∼520 pC/N, TC∼ 205°C) for this composition was similar to that of ceramics where x= 0.08, y= 0, which had a TC of ∼250°C.

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